Adjustable lighting apparatus

ABSTRACT

In one exemplary embodiment, a remote controlled adjustable dental operating light is provided that projects a light beam having an elongated cross-sectional configuration with the horizontal width being large in comparison to the vertical height of the beam. A pair of light sources each project a beam having an elongated cross-section, the two beam being longitudinally aligned and overlapping to form a single composite beam having an elongated cross-sectional configuration. The light beams are reversibly pivotable about a rotatable axis to adjust the central axis of the light beam to properly illuminate the patient&#39;&#39;s mouth. Shields provided over a portion of the external area of the light sources mask the bright filaments from the patient&#39;&#39;s eyes.

United States Patent Alger 15 1 ADJUSTABLE LIGHTING APPARATUS [72] Inventor: David W. Alger, 101 Pine Shadow,

Conroe, Tex. 77301 [22] Filed: March 22, 1971 21 Appl.No.: 126,792 I Related US. Application Data [63] Continuation of Ser. No. 770,578, Oct. 25,

1968, abandoned.

[52] US. Cl. ..240/ 1.4, 240/41.15, 240/44.27, 240/41.6 [51] Int. Cl. ..H61g 13/00, F21v 33/00 [58] Field of Search ..240/l.4,41.15,4l.4,41.55, 240/44.27, 41.6, 44, 46.33, 46.35, 46.45,

[56] References Cited UNITED STATES PATENTS 1,162,660 11/1915 Shirreffs ..240/414 1,397,822 11/1921 Peters ..240/46.45 X 1,678,408 7/ 1928 Tumey, Sr. ..240/41.4 2,280,402 4/1942 Greppin ..240/41. 15 2,846,566 8/1958 Gunther et a1 ..240/1.4

[ Nov. 14, 1972 2,911,519 11/1959 Phillips et al. ..240/1 .4 2,911,525 11/1959 Strorn ..240/4l.15 3,287,552 11/1966 Drandell ..240/41.l5

Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard M. Sheer Attorney-Frank S. Vaden, III et al.

I 57 ABSTRACT In one exemplary embodiment, a remote controlled adjustable dental operating light is provided that projects a light beam having an elongated cross-sectional configuration with the horizontal width being large in comparison to the vertical height of the beam. A pair of light sources each project a beam having an elongated cross-section, the two beam being longitudinally aligned and overlapping to form a single composite beam having an elongated cross-sectional configuration. The light beams are reversiblypivotable about a rotatable axis to adjust the central axis of the light beam to properly illuminate the patients mouth. Shields provided over a portion of the external area of the/light sources mask the bright filaments from the patients eyes.

10 Claims, 7 Drawing Figures PKTENTED 14 I97? 3. 702.928

SHEET 1 or 2 v EH N David W. Alger INVENTOR B 19 20 B Y M 1 FIG.2 W a; 0M

' I ATTORNEYS PATENTEDuuv 14 m2 3.702.928

sum 2 or 2 David W. Alger v INVENTOR ATTORNEYS FIG.7

ADJUSTABLE LIGHTING APPARATUS CROSS-REFERENCE TO RELATED APPLICATION The instant patent application is a continuation of application, Ser. No. 770,578, now abandoned, entitled Adjustable Lighting System filed Oct. 25, 1968 in the name of David W. Alger as inventor.

BACKGROUND OF THE INVENTION In modern dental operations, many advances in equipment design have been made in recent years. New' reclining contoured chairs have been designed that are more comfortable for the patient and easier to operate by the dentist. I-Iigh-speed air drills have replaced the clumsy belt driven drills of the past. The old dental units which supported a multi-armed dental operating light, the electric-driven drill, a cuspidor, water, suction devices and provided for other attachments has been replaced in many dental offices by a compact console which does not have the typical multi-armed dental operating light.

The old multi-armed dental light was inconvenient for the patient as well as the dentist. The light had to be repositioned each time to allow the patient to get out of the chair. The dentist had to be constantly moving the light to a new position to obtain different views of the patients mouth, which was annoying and time consum ing. In addition, the dentist had to use his hand to reposition the conventional light unit, thus leaving only one hand continuously free and creating a sterility hazard by having to touch the lightwhile performing the dental operations.

It is generally not feasible for an assistant to position the light since it is extremely difficult to do so to the doctor's satisfaction for the view that he is seeking of the patients mouth. Use of the conventional light is a strictly trial anderror operation to obtain the desired illumination. When using the newer consoles, many doctors attempted to mount the conventional light on the flooror wall, but the same problems were encountered.

Other lighting systems found in the prior art, such as remotely controlled surgical operating lights are not feasible for use in a typical dental office. Further, these lights are generally quite large in size and were designed to illuminate an extremely large area. Further, they generate a great deal of radiated heat that would cause discomfort to the patient and the doctor in the confines of a dentists office. The fixed ceiling mounted lighting systems are not practical since a dental operatin g light must be capable of being repositioned for each individual patient and because of the varying dental operations to be performed.

One prior art device has made a stride in the proper direction. Such a dental operating light is a remote controlled lighting system that provides a plurality of high intensity light beams that are focused to a desired focal point within the patients mouth. The light sources are mounted in a housing secured to the ceiling of the dental office and the beams may be positioned upwardly or downwardly by remote control to adjust the height of the light beam for patients of varying heights and sizes. Such an improved lighting system is disclosed in a US. Pat. to J. Drandell, No. 3,287,552, entitled Remote Controlled Lighting System, issued Nov. 22, 1966.

However, the Drandell lighting system has several serious drawbacks. In the Drandell system the plurality of light beams are focused to a point within the patients mouth, and if the dentist desires to move the chair laterally the patients mouth is moved out of the lighted area. This limits the dentist in his movement of the chair to only various reclining positions longitudinally aligned with the focused light beam. Further, if the dentist desires to remove dental work, such as crowns, bridges and the like from the patients mouth for examination, the doctor will either have to have an additional light to enable him to examine the dental work or he will have to hold the dental work up in front of the patients face to examine the work in the projected light beam. In addition, the high intensity light beams, although they are positioned to converge at a focal point at the patients mouth, are uncomfortable for thepatients eyes since he receives considerable glare and direct light from the light sources.

The present invention remedies the problems of the prior art by rotatably mounting the light sources for movement about a fixed rotational axis, and projecting light beams having a rectangular vertical cross-section positionable to illuminate the patients mouth when seated in the dental chair. The width of the light beam is large compared to its height, allowing the light beam to extend beyond the sides of the patients face for providing illumination of dental work outside of the patients mouth, and to allow lateral movement of the dental chair without having to reposition the light beam.

SUMMARY OF THE INVENTION The instant invention provides a novel adjustable dental operating light positionable about a single axis but providing a light beam having a rectangular vertical cross-section with a large widthdimension compared to the height of the beam.

In the preferred embodiment, the light sources are motor-driven and controls in the form of push-button switches are mounted on the floor adjacent to the dental chair for allowing ready accessibility by the dentist for actuating the motor and positioning the light beam while leaving both hands of the dentist free for performing dental operations within the patients mouth. A magnetic brake device is provided which instantaneously stops the movement of the motor as soon as it is deenergized in order to prevent overshooting of the light beam from its desired position.

The lighting system is designed to be mounted upon the ceiling, on a wall, or recessed flush with the ceiling. Other mounting arrangements could, of course, be utilized as desired by the doctor and depending on the layout of his office.

Accordingly, one primary feature of the present invention is to provide an adjustable dental lighting system which may be precisely and easily controlled and which is capable of providing a light beam having an elongated cross-section for illuminating the patients mouth.

Another primary feature of the present invention is to provide a dental lighting system which is capable of providing a light beam having an elongated cross'section for providing illumination to either side of the patients head to enable the doctor to examine dental work removed from the patients mouth.

Yet another primary feature of the present invention is to provide a dental lighting system which is capable of providing a light beam having an elongated crosssection for illuminating the patients mouth and extending to either side of the patients head to allow the doctor to move the dental chair laterally without having to reposition the light.

Still another feature of the present invention is to provide a dental lighting system in which a portion of the light source is shielded for minimizing patient discomfort due to direct light and glare.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the manner in which the above-recited advantages and features of the invention are attained, as well as others which will become apparent can be understood in detail, a more particular description of the invention may be had by reference to specific embodiments thereof, which are illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the ap pended drawings illustrate only typical embodiments of the invention and therefore are not to be considered limiting of its scope for the invention may admit to further equally effective embodiments.

In the Drawings:

FIG. 1 is a perspective view showing the adjustable dental operating light system projecting a light beam onto a patient seated in a dental chair.

FIG. 2 is a cross-sectional view of the light beam projected by the lighting system and showing the positioning of the light beam with relation to the patients face.

FIG. 3 is an enlarged perspective view of the adjustable dental operating light system with the unit in an operating position.

FIG. 4 is a bottom view of a preferred embodiment of the lighting system with a fragmentary portion of the enclosure cut away for showing the location of the drive motor.

FIG. 5 is an enlarged fragmentary detail view of a portion of the light unit showing the direct connection of the electric motor to the support member for rotationally adjusting the light unit.

FIG. 6 is a partial vertical cross-sectional view of the adjustable dental operating light unit showing the mounting of the sealed beam lamps within the supporting member.

FIG. 7 is a schematic wiring diagram of the adjustable dental operating system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, a preferred embodiment of the adjustable dental operating light system 10 is shown attached to the ceiling 12 of a dentists office by any suitable attaching means such as screws or bolts (not shown). Two light beams 14 and 16, are shown as being projected across the lower facial portion, including mouth 20, of a patient seated in a dental chair 22. Light beams 14 and 16 have an elongated cross-section, and are longitudinally aligned and overlap to form a single composite beam 18 having a rectangular vertical crosssection, wherein the central portion of beam 18 is an area of reinforced light as will be hereinafter explained.

For convenience, dental operating system 10 may be remotely controlled by means of push-button switches located on the floor of the dentists office adjacent chair 22, as shown by switches 24, 26 and 28. In this arrangement, switch 28 is an on-off switch and switches 24 and 26 are utilized for actuating the light system and sweeping or adjusting the light beam 18 either up, as shown by the arrow A, or down, as shown by the arrow B, to properly illuminate the patients mouth. In the preferred embodiment of the invention, the switches 24 and 26 are of the push-button type so as to adjust the light beam 18 either up or down when the switches are depressed and to stop the motion of the light beam when the switch is released. In the configuration shown, the dentist would be able to operate switches 24, 26 and 28 as foot switches, thereby freeing both hands for handling dental instruments and performing dental operations on the patient.

Alternatively, the operating switches for the dental operating light system 10 could be located on the side of the dental chair, or they could be located in any other convenient location, and utilize either push-button type switches or toggle switches shown as 25 and 28a in FIG. 1. Toggle switch 25 may conveniently be a double-pole double-throw switch for sweeping the light beam 18 upwardly or downwardly as shown by the arrows A and B, respectively. Switch 28a is an on-off switch for performing the same function as the pushbutton counterpart 28.

Referring now to FIG. 2, a cross-sectional view of light beams l4, l6 and 18 is shown superimposed over the lower facial area of the patient. Each of the light beams 14 and 16 have an elongated horizontal crosssection, are longitudinally aligned, and longitudinally overlap to form a single composite light beam 18 having a rectangular vertical cross-section. The central area 19 of the composite light beam 18, where light beams 14 and 16 overlap, is an area of greater light intensity that may be adjusted upwardly or downwardly, shown by arrows A and B respectively, to cover the patients lower facial area and approximately centered on the patients mouth 20. This narrow area of high intensity light provides a brilliant operating light free of shadows for illuminating the patients mouth during dental operations.

Since the beam has a narrow vertical height, the light may be raised or lowered as shown by the arrows A and B, respectively, to accommodate various sizes and heights of patients and varying reclining positions of the patient within the dental chair 22 (see FIG. 1). Direct light and glare are eliminated by use of the narrow-height beam. However, because the composite beam 18 has a wide horizontal width, it extends outwardly beyond the patients face on either side. The dentist may remove plates, partial bridgework, crowns or other dental handwork from the patients mouth for convenient viewing and examination immediately adjacent the patients head. In addition, the broad horizontal width of the light beam 18 allows the dental chair 22 (see FIG. 1) to be rotated laterally, either to the left or right and the patients mouth may still be kept within the horizontal and vertical limits of light beam 18.

The adjustable dental operating light system 10 is shown in greater detail in FIG. 3. The light system is housed by an enclosure 30 made of a light weight sheet metal having a high temperature-resistant baked-on enamel finish. In the bottom face of enclosure 30 is a rectangular opening 33 within which is rotationally mounted a rectangular supporting frame 32 having a pair'of elongated openings 36 having the configuration of a chordal segment of a circle, the upper side or portion 37 of each opening defining a straight line. Sealed beam light units 38 are mounted behind the elongated openings 36 and the upper two-thirds of the light units are shielded by a curved shield 34 that is formed to accommodate the curved surface of the lens of light units 38. General Electric sealed beam lamp units, Numbers 4502 and 4505 have been advantageously used in the dental light application. The Nos. 4505 and 4502 lamp units provide the desired elongated light beam, the No. 4502 unit providing a beam measuring approximately 3X36 inches, and the No. 4505 unit providing a beam measuring approximately 3X18 inches. Shield 34 blocks the sealed beam filament from the patients eyes, thereby eliminating a source of discomfort for the patient during the dental operation.

The lower edges 37 of shield 34 (the upper edge 37 of openings 36) also serve to sharply define and straighten the. top edge of the composite light beam projected by the lamps 38 in order to assist the dentist in correctly positioning the light beam and to further aid patient comfort by eliminating glare from the patients eyes.

The supporting frame member 32 mounting the sealed beam units 38, as hereinabove mentioned, is rotationally suspended within the aperture 33 of housing 30. A reversible drive motor through a reduction gearbox (not shown) rotates frame 32 and the attached sealed beam units 38. The rotation of frame 32 sweeps the composite light beam 18 in an arc (see FIG. 2), for the proper desiredposition on the patients face. The sealed beam units 38 are suitably mounted on support member 32 to place the axes of the projecting light beams 14 and 16 in a substantially parallel relationship.

A switch 39 is provided for varying the intensity of the light beam from light units 38. In the preferred embodiment shown, a three-position switch has been provided, although it is apparent that a switch having a greater number of positions or one being continuously variable may be provided without departing from the scope of the invention. An accessory jack 40, providing 6 volts AC, is provided for powering instrumentstsuch as an operating headlight often used by many oral surgeons and other dental specialists.

Referring now to FIGS. 1, 2 and 3, the lighting system 10 is advantageously mounted to the ceiling of the dentists office and positioned to intersect an imaginary line which would bisect the angle between the upper and lower dental arches of the patient in a customary working position in chair 22. The center of the distance between the adjacent elongated openings 36 would, in a preferred installation, lie within a vertical plane passing through the longitudinal centerline of chair 22 in its usual working position. With such a preferred installation, the horizontal width of the beam at the chair would be approximately 2 to 4 feet and the vertical height would be approximately 3 inches.

More than two light units 38 may be utilized to increase the horizontal width of the beam or to increase the intensity of the central area 19 of beam 18. However, it will be apparent that only one lamp unit 38 may just as effectively be utilized, although the horizontal width of light beam 18 will be somewhat shortened.

Referring to FIGS. 4, 5 and 6, supporting frame member 32 is shown supporting two sealed beam light units 38 held in place by means of any suitable attaching device, such as the spring clamps 56. A pair of outwardly projecting circular areas are provided in the face of member 32 for accepting the face of the circular sealed beam light units38. The lower portion of the circular areas in the face of member 32 is cut away to form an elongated opening having a configuration of a chordal segment of a circle. The upper portion 34 of the outwardly protruding circular area is left intact to cover approximately the upper two-thirds of the sealed beam light unit 38 and acts as a shield to block direct light from the filament of the light source from the pa tients eyes, thereby cutting glare to a maximum extent.

Attached to each longitudinal end of the supporting member 32 is an extending arm member 52. Arm members 52 are removably fixed to shafts 42 and 44 by means of set screws 54. An electrical motor 46 and a reduction gear box 47 are suitably mounted within enclosure 30 and directly coupled to shaft 44. Shaft 42 is rotatably supported within enclosure 32 by means of insertion throughan aperture in an upright wall (not shown), identical to wall 31 adjacent to motor 46 and gearbox 47, and allows supporting member 32 to pivot about rotational axis 43. A magnetic brake 48 is adapted for instantaneously stopping the movement of drive shaft 44 when the motor 46 is de-energized, thus preventing overrun by the supporting member 32 when the light beam has been positioned as desired.

A transformer 50 is suitably mounted within enclosure 30 by any suitable means such as screws or bolts, (not shown) and provides suitable stepdown voltages from a standard I 10-1 15 volt AC source for the operation of the lamp units 38 and accessory jack 40. The placement of transformer 50, motor 46 and gear box 47, and associated brake 48, lamp units 38, the light intensity switch 39 and the accessory jack 40 are shown in their physical relationship without the necessary interconnecting wiring, which will be hereinafter discussed.

For mounting purposes, a transverse channel member 35, connected between opposite longitudinal ends of enclosure 30 is provided for suitably attaching the light system 10 to a ceiling or wall or any other suitable surface by means of screws or bolts (not shown). Of course, the system 10 may be recessed into the ceiling for a flush-type mounting.

FIG. 7 is a schematic wiring diagram for the light system 10. A source of AC voltage (commonly l lO-l 15 volts AC) is applied to one side of the primary winding 51 of transformer 50 via conductor 60, and to the other side via conductor 62, on-off switch 28, and conductor 61. Input line voltage is also applied via conductors 60, 72, 73 and 74 to one terminal of threepoint make push-button switches 24 and 26, respectively. The secondary winding 52 of transformer 50 has three primary taps for providing lower voltages, preferably 25-27-29 volts AC via conductors 66, 65 and 64, respectively, to the light intensity switch 39. The selected secondary voltage of transformer 50 is ap plied via one of conductors 66,65 and 64 to switch 39 and thence through wires 69 and 70) to the parallel connected filaments of lamps 38. The other side of the filaments of lamps 38 are connected through conductor 63 to the other side of secondary winding 52.

Light intensity switch 39 is provided to vary the intensity of lamps 38. In performing dental operations, it may be desired to vary the intensity of the light depending on other office lighting conditions and the desired light intensity necessary for a particular examination of the patients mouth. However it has been found that a particular light intensity, once selected for the lighting conditions available, need not be changed unless the line voltage varies or office lighting conditions change.

When switch 24 is closed, line voltage is applied via conductors 60, 72 and 73 through switch 24 to motor 46 via conductor 76. The circuit is completed from motor 46 through conductors 81 and 61, and switch 28 to line voltage through wire 62 for energizing motor 46. When switch 24 is closed, line voltage is also applied through switch 24 via conductor 75 to one side of coil 79 of the magnetic brake device 48, and the other side of coil 79 is connected to conductor 81 by wire 80 for energizing coil 79 and disengaging brake means 49 for releasing the shaft of motor 46.

When switch 24 is released, line voltage is removed from conductors 75 and 76, thereby de-energizing motor 46 and the electromagnetic coil 79 of the brake device 48, allowing the brake means 49 to engage the shaft of motor 46 causing it to stop instantaneously. When switch 26 is depressed, line voltage is applied from conductor 74 through switch 26 and conductors 78 and 75 to coil 79, thereby energizing the coil as hereinbefore described and disengaging the brake means 49 from the'shaft of motor 46. Line voltage is also applied via conductor 74, switch 26 and conductor 77 to motor 46 for energizing motor 46 and causing it to be rotated in an opposite direction than that previously described when switch 24 was actuated. When switch 26 is released, the motor 46 and the electromagnetic coil 79 are de-energized and brake means 49 instantaneously stops the rotational motion of motor 46.

In operation, switch 24 would be utilized to rotate the light units 38 mounted on the supporting frame member 32 upwardly by rotating member 32 about rotational axis 43. As switch 24 is released, the magnetic brake device 48 instantaneously stops the motor and the support member 32 carrying the light units 38 in the desired position. Similarly, switch 26 may be utilized to rotate the motor in a reverse direction and rotate support member 32 downwardly to re-position the light beams.

As hereinabove described, the intensity of the light emitted by each of the sealed beam units may be varied by means of the light intensity switch 39. The supporting member has a special heat resistant baked-on enamel finish to withstand the intense heat from the sealed beam light units, however, any other suitable finish capable of resisting the high temperature associated with such sealed beam units may be employed.

Numerous variations and modifications may obviously be made in the structure herein described without departing from the present invention. Accordingly, it should be clearly understood that the forms of the inventions herein described and shown in the figures of the accompanying drawings are illustrative only and are not intended to limit the scope of the invention.

What is claimed is:

l. A dental operating light for projecting a light beam having a generally rectangular vertical cross-section,

comprising an enclosure, an elongated rotatable member having a pair of longitudinally aligned spaced-apart elongated openings, the upper side of each of which defines a straight line, and adapted for rotational movement with respect to said enclosure about an axis of rotation,

a pair of light units each of which is capable of projecting a light beam having a generally rectangular vertical cross-section, the width of said beams being greater than the height of said beams,

attaching means for attaching each of said light units to said rotatable member adjacent one of said elongated openings for projecting therethrough a pair of light beams, each having said generally rectangular vertical cross-section, said light units being positioned to cause said light beams to centrally overlap to form a single composite light beam having a generally rectangular vertical crosssection, with a central portion thereof being of a brighter intensity than the end portions thereof,

a reversible electric motor mounted within said enclosure,

a gearbox directly coupling said motor and said elongated rotatable member for rotating said rotatable member about said axis of rotation when said motor is energized and sweeping said composite light beam in an arc to a selected position,

switch means for reversibly energizing said motor,

and

means adapted for instantaneously braking said motor upon de-energization thereof for stopping the rotation of said elongated'rotatable member and said composite light beam at a selected position.

2. The apparatus as described in claim 1, wherein said elongated openings have a generally rectangular configuration.

3. The apparatus as described in claim 1, wherein said elongated openings have the configuration of a chordal segment of a circle.

4. The apparatus as described in claim 1, wherein a portion of each of said light units is masked by a portion of said elongated rotatable member adjacent said elongated openings for shielding the filaments of said light units.

5. The apparatus as described in claim 1, wherein the upper straight line side of each of said elongated openings acts to sharpen and straighten the upper side of said projected rectangular light beams.

6. The apparatus as described in claim 1, wherein the axes of said projecting light beams are positioned in a substantially parallel relationship.

7. The apparatus as described in claim 1, including means for selectively varying the intensity of said plurality of light units.

8. A dental light for projecting a light beam having a rectangular vertical cross-section upon the mouth of a seated patient, comprising an enclosure,

an elongated support member having a pair of longitudinally aligned spaced-apart elongated openings, the upper side of each of which defines a straight line, said support member having a pair of speed reducing means interconnecting said motor extending arms, I and said first shaft for imparting rotational motion first and second shafts connected to respective ones to said support member about said axis of rotation of said pair of extending arms and mounted within when said motor is energized and sweeping said said enclosure for allowing rotational movement of elongated cross-sectional composite light beam said support member about an axis of rotation, through an arc about said axis to a selected posia pair of light sources each of which is capable of tion,

projecting a light beam having a generally rectanbrake means mounted on said motor for instantanegular vertical cross-section, the width of said ously stopping the rotational movement of said beams being greater than the height of said b a support member when said motor is de-energized, attachment means for attaching each of said light first Switch means for le ti ely e e gizing Sai sources to said support member adjacent one of l'evelsiblfi motor, and

said pair of elongated openings respectively for Second Switch means for Selectively Varying the projecting therethrough a pair of beams of light, tensity of said pair of beamed-light sources.

each of said beams having a rectangular vertical The apparatus as desCribed l Claim 8, wherein a cross-section and longitudinally overlapping to Porticm of each of Said light units 15 y a P}" form a single composite light b h i a tion of said elongated rotatable member ad acent sa d rectangular vertical cross-section, said composite Openmgs for Shleldmg the filamems of 531d light beam having a central portion of greater in- 8 unlist i h h d portions th f 10. The apparatus as described in claim 8, wherein th axes f id i f projecting light beams being the upper straight line slde of each of said elongated in spaced substantially parallel relationship, operlmgs a to sharpen and straighten the upper slde a reversible motor mounted within said enclosure adof sad Pm-lected rectangular hght beamsjacent to said first shaft, a: t 

1. A dental operating light for projecting a light beam having a generally rectangular vertical cross-section, comprising an enclosure, an elongated rotatable member having a pair of longitudinally aligned spaced-apart elongated openings, the upper side of each of which defines a straight line, and adapted for rotational movement with respect to said enclosure about an axis of rotation, a pair of light units each of which is capable of projecting a light beam having a generally rectangular vertical crosssection, the width of said beams being greater than the height of said beams, attaching means for attaching each of said light units to said rotatable member adjacent one of said elongated openings for projecting therethrough a pair of light beams, each having said generally rectangular vertical cross-section, said light units being positioned to cause said light beams to centrally overlap to form a single composite light beam having a generally rectangular vertical cross-section, with a central portion thereof being of a brighter intensity than the end portions thereof, a reversible electric motor mounted within said enclosure, a gearbox directly coupling said motor and said elongated rotatable member for rotating said rotatable member about said axis of rotation when said motor is energized and sweeping said composite light beam in an arc to a selected position, switch means for reversibly energizing said motor, and means adapted for instantaneously braking said motor upon deenergization thereof for stopping the rotation of said elongated rotatable member and said composite light beam at a selected position.
 2. The apparatus as described in claim 1, wherein said elongated openings have a generally rectangular configuration.
 3. The apparatus as described in claim 1, wherein said elongated openings have the configuration of a chordal segment of a circle.
 4. The apparatus as described in claim 1, wherein a portion of each of said light units is masked by a portion of said elongated rotatable member adjacent said elongated openings for shielding the filaments of said light units.
 5. The apparatus as described in claim 1, wherein the upper straight line side of each of said elongated openings acts to sharpen and straighten the upper side of said projected rectangular light beams.
 6. The apparatus as described in claim 1, wherein the axes of said projecting light beams are positioned in a substantially parallel relationship.
 7. The apparatus as described in claim 1, including means for selectively varying the intensity of said plurality of light units.
 8. A dental light for projecting a light beam having a rectangular vertical cross-section upon the mouth of a seated patient, comprising an enclosure, an elongated support member having a pair of longitudinally alIgned spaced-apart elongated openings, the upper side of each of which defines a straight line, said support member having a pair of extending arms, first and second shafts connected to respective ones of said pair of extending arms and mounted within said enclosure for allowing rotational movement of said support member about an axis of rotation, a pair of light sources each of which is capable of projecting a light beam having a generally rectangular vertical cross-section, the width of said beams being greater than the height of said beams, attachment means for attaching each of said light sources to said support member adjacent one of said pair of elongated openings respectively for projecting therethrough a pair of beams of light, each of said beams having a rectangular vertical cross-section and longitudinally overlapping to form a single composite light beam having a rectangular vertical cross-section, said composite light beam having a central portion of greater intensity than the end portions thereof, the axes of said pair of projecting light beams being in spaced substantially parallel relationship, a reversible motor mounted within said enclosure adjacent to said first shaft, speed reducing means interconnecting said motor and said first shaft for imparting rotational motion to said support member about said axis of rotation when said motor is energized and sweeping said elongated cross-sectional composite light beam through an arc about said axis to a selected position, brake means mounted on said motor for instantaneously stopping the rotational movement of said support member when said motor is de-energized, first switch means for selectively energizing said reversible motor, and second switch means for selectively varying the intensity of said pair of beamed-light sources.
 9. The apparatus as described in claim 8, wherein a portion of each of said light units is masked by a portion of said elongated rotatable member adjacent said elongated openings for shielding the filaments of said light units.
 10. The apparatus as described in claim 8, wherein the upper straight line side of each of said elongated openings acts to sharpen and straighten the upper side of said projected rectangular light beams. 